A phase II study of capecitabine plus concomitant radiation therapy followed by durvalumab (MEDI4736) as preoperative treatment in rectal cancer: PANDORA study final results.
Authors: Stefano Tamberi, Elisa Grassi, Chiara Zingaretti, Giorgio Papiani, Sara Pini, Jody Corbelli, Maria Di Bartolomeo, Filippo Pietrantonio, Giovanni Luca Frassineti, Alessandro Passardi, Fabio Gelsomino, Marina Marzola, Maria Banzi, Andrea Vincent Bonetti, Elisabetta Petracci, Chiara Carli Moretti, Isabella Banchelli, Davide Tassinari, Giampaolo Ugolini, Oriana Nanni
Journal: Journal of Clinical Oncology (2022)

LBA3513 Background: The combination of capecitabine plus long course radiotherapy (RT) is the standard preoperative therapy in cT3-4 cN+ rectal cancer. pathologic complete remission (pCR) can be considered as surrogate endpoint of efficacy of treatment in terms of disease-free survival (DFS). Preclinical data points heavily toward a strong synergy between RT and immune treatments. Methods: This is a prospective phase II, open label, single arm, multicentre study in patient with locally advanced rectal cancer who receive standard concomitant CT/RT therapy (825 mg/m2 twice daily capecitabine every day and 5040 cGy radiotherapy for 5 days per week for 5 weeks) followed by durvalumab (1500 mg Q4W for 3 administrations). Surgery is performed after 10-12 weeks from neoadjuvant therapy. The primary endpoint is the proportion of pCRs after at least 1 cycle of durvalumab; secondary endpoints are the proportion of clinical complete remissions (cCRs) after at least 1 cycle of durvalumab, the proportion of adverse and serious adverse events (NCI CTCAE v5.0). The sample size has been estimated by using the optimal Simon’s two-stage design assuming a null pCR proportion of 0.15 and an alternative pCR percentage of 0.30 (alpha = 0.05, power = 0.80). If more than 4 pCRs were observed in the first 19 enrolled patients, 36 additional patients were to be accrued for a total of 55 evaluable patients. The null hypothesis is rejected if ≥ 13 pCRs are observed in 55 patients. Results: Between November 2019 and August 2021, 60 patients were accrued, of which 55 were evaluable for study objectives. Fifty-two of 55 treated patients received all 3 infusions of durvalumab. After treatment, a clinical response percentage of 81.8% was observed; 3 patients had progression of disease due to local and/or metastases before surgical intervention. Eighteen patients achieved complete pathological response (32.7%), confirmed by central revision. Near complete regression, moderate and minimal regression were observed in 14 (25.5%), 9 (16.4%) and 11 (20.0%) patients respectively. Regarding toxicity, 23 patients (41.8%) had adverse events (AEs) related to durvalumab treatment. Two patients (1.8%) discontinued durvalumab for toxicity. Grade 3 AEs occurred in 4 (7.3%) patients (diarrhea, skin toxicity, transaminase increase, lipase increase and pancolitis). No Grade 4 toxicity was observed. In 20 patients (36.4%) G1-2 AEs related to durvalumab were observed. The most common were endocrine toxicity (hyper/hypo-thyroidism), dermatologic toxicity (skin rash) and gastrointestinal toxicity (transaminase increase, nausea, diarrhea, constipation). Conclusions: This study met its primary endpoint showing a promising activity of neoadjuvant chemo-radiotherapy plus durvalumab in terms of pCR rate and a safe toxicity profile. Clinical trial information: NCT04083365.